It is sometimes desirable to include agents, such as quaternary onium salts, silver ions, iodine ions, and the like, into coatings in order to provide a surface that is capable of killing harmful microorganisms.
Silver ions, for example, are sometimes embedded in a porous material, such as zeolite, which is incorporated into a coating composition. In these situations, the silver ions are released gradually into the coating to impart antimicrobial properties, but the eventually depletion of the silver ions will ultimately render the coating ineffective. Moreover, a significant problem associated with such antimicrobial agents is their tendency to cause discoloration of the composition into which they are incorporated. This discoloration results from the interaction of silver ions with other compounds, ions, and the like present in the composition into which the antimicrobial agent is incorporated. As will be appreciated, such discoloration can be particularly problematic in coatings applications where decorative properties are often critical.
Quaternary onium salts can be effective antimicrobial agents in coating compositions, because they are known to selectively attack bacterial cells and not mammalian cells. Unfortunately, these materials are typically unreactive with the primary film forming resin binder of the coating composition, such as resins containing carboxylic acid groups, which are often employed in thermosetting compositions. As a result, such onium salts are susceptible to leaching out of or phase separating from the binder, thereby rendering the onium salt ineffective and/or the coating composition unsuitable for use for other reasons.
As a result, it would be desirable to provide antimicrobial coating compositions that include an antimicrobial agent that will not be depleted and will not phase separate in a coating composition comprising a film-forming resin binder having functional groups. The present invention has been developed in view of the foregoing desire.